Method for manufacturing semiconductor device

ABSTRACT

The present invention is a separation method for easy separation of an allover release layer with a large area. Further, the present invention is the separating method that is not subjected to restrictions in the use of substrates, such as a kind of substrate, during forming a release layer. A separation method comprising the steps of forming a metal film, a first oxide, and a semiconductor film containing hydrogen in this order; and bonding a support to a release layer containing the first oxide and the semiconductor film and separating the release layer bonded to the support from a substrate provided with the metal layer by a physical means. Through the separation method, heat treatment is carried out to diffuse hydrogen contained in the semiconductor film, a third oxide is formed by reducing a second oxide formed at a surface boundary between the metal film and the first oxide film, and a film containing the second oxide and the third oxide, a surface boundary between the film containing the second oxide and the third oxide, and the metal film, or a surface boundary between the film containing the second oxide and the third oxide, and the first oxide is split.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for separating a releaselayer. Specifically, the present invention relates to a method forseparating a release layer including various devices. And morespecifically, the present invention relates to an electric applianceincluding a display apparatus as typified by a liquid crystal module, anEL (electroluminescent) module, or the like, as one of components.

2. Related Art

In recent years, a technique for forming a TFT composed of asemiconductor thin film (with a thickness of approximately from severalto several hundreds nm) formed over an insulating surface of a substratehas attracted attention. TFTs are used for an electric device such asIC, an electro-optic device, or the like, and are especially developedas a switching device or a driver circuit of a display apparatus.

In such a display apparatus, a glass substrate and a quartz substrateare generally used, however, they have disadvantages such as beingfragile and heavy. In addition, the glass substrate and the quartzsubstrate are difficult to grow in size for mass-production. Hence, itis attempted that a TFT device is formed over a substrate havingflexibility as typified by a flexible plastic film (a plasticsubstrate).

However, in case of using a high performance polysilicon film for theactive layer of a TFT, a high temperature process at several hundredsdegrees is required for a manufacturing process, so that a TFT cannot bedirectly formed on a plastic film.

Therefore it has already been proposed a separating method forseparating a release layer, which is formed over a substrate via aseparating layer, from the substrate. For example, a separation layerformed of amorphous silicon (or polysilicon) is formed, and hydrogencontained in the amorphous silicon is released by laser lightirradiation through a substrate to produce a space, then the substrateis separated (See reference 1: Unexamined Patent Publication No.10-125929). In addition, Reference 2 (Unexamined Patent Publication No.10-125930) discloses that a liquid crystal display apparatus iscompleted by pasting a release layer (referred to as a transferred layerin the reference) to a plastic film by means of the technique disclosedin Reference 1.

However, the above-described method requires a substrate that is verytransparent to light, and comparative large amount of laser lightirradiation for energizing enough to release hydrogen contained inamorphous silicon, so that a problem becomes arisen that a release layeris damaged. In addition, according to the above described method, incase of forming a device over a separation layer and carrying out heattreatment or the like at high temperature during a manufacturingprocess, there is a threat that separation is inadequately carried outeven if a laser light is emitted to a separation layer since hydrogencontained in the separation layer is decreased due to the heattreatment. Accordingly, processes after forming a separation layer maybe restricted in order to keep the amount of hydrogen contained in theseparation layer. There is the description in above references that alight-shielding layer or a reflection layer is provided in order toprevent a release layer from being damaged, in such a case, it isdifficult to manufacture a transparent liquid crystal display apparatusor a light-emitting display apparatus of bottom emission type.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a separation method for easy separation of an allover releaselayer with a large area. A further object of the present invention is toprovide the separating method that is not subjected to restrictions inthe use of substrates, such as a kind of substrate, during forming arelease layer.

For solving the above described problems, the following measures aretaken in the present invention.

The present invention is a separation method for easy separation of anallover release layer with a large area. Further, the present inventionis the separating method that is not subjected to restrictions in theuse of substrates, such as a kind of substrate, during forming a releaselayer. A separation method comprising the steps of forming a metal film,a first oxide, and a semiconductor film containing hydrogen in thisorder; and bonding a support to a release layer containing the firstoxide and the semiconductor film and separating the release layer bondedto the support from a substrate provided with the metal layer by aphysical means. Through the separation method, heat treatment is carriedout to diffuse hydrogen contained in the semiconductor film, a thirdoxide is formed by reducing a second oxide formed at a surface boundarybetween the metal film and the first oxide film, and a film containingthe second oxide and the third oxide, a surface boundary between thefilm containing the second oxide and the third oxide, and the metalfilm, or a surface boundary between the film containing the second oxideand the third oxide, and the first oxide is split.

As the metal film, an element selected from the group consisting of W(tungsten), Ti (titanium), Mo (molybdenum), Cr (chrome), Nd (neodymium),Fe (iron), Ni (nickel), Co (cobalt), Zr (zirconium), Zn (zinc), Ru(ruthenium), Rh (rhodium), Pd (palladium), Os (osmium), Ir (iridium); asingle layer formed of an alloy material or a compound material each ofwhich contains the above elements as its main components; or alamination layer formed of these metals or mixture of these metals areused. The first oxide is formed of an insulating film such as a siliconoxide film. The second oxide is formed naturally during forming thefirst oxide over the metal film by sputtering, but can also be formed bythermal oxidation. The second oxide is sometimes disappeared byreductive reaction due to hydrogen contained in the first oxide. Thus,the first oxide is preferably formed not to contain hydrogen. Further, asemiconductor film containing hydrogen can be formed by CVD, and can bereplaced with a nitride film containing hydrogen, since both of thefilms disperse hydrogen contained therein by heat treatment.Accordingly, the film that disperses hydrogen by heat treatment ispreferably used since peeling is carried out by reductive reaction dueto hydrogen in the present invention. The heat treatment is preferablycarried out at 400° C. or more. The temperature of 400° C. is the limitof acceptable temperature for carrying out separation. In addition, heattreatment is not always necessary for crystallization of the material ofthe metal film, for example, molybdenum is crystallized without heattreatment.

The release layer includes an oxide film and a semiconductor filmcontaining hydrogen. A base film is preferably formed at a surfaceboundary between the oxide film and the semiconductor film. As the basefilm, a silicon oxynitride film or a silicon nitride oxide film ispreferably used.

A transistor that uses a semiconductor film as an active layer and adevice that is connected to the transistor are preferably formed beforeseparation. Given examples of the device: a semiconductor device, alight-emitting device, a liquid crystal device, or the like. Further,the separated release layer is preferably bonded to a new substrate. Incase of bonding the release layer to a plastic substrate, a TFTsubstrate that is thin, hardly broken even if it falls, and lightweightcan be formed.

The material for forming the metal film may have some defects in thecrystal structure due to inside and outside factors. The valance numberis various. The material becomes into various compounds by bonding to anatom of oxygen or hydrogen.

In compounds (non-stoichiometric compounds) used for the metal film suchas tungsten oxide (WO_(3-X)), molybdenum oxide (MoO_(3-X)), or titaniumoxide (TiO_(2-X)), defects are disappeared by the process ofcrystallographic shear (CS), that is, linkage of some octahedrons ischanged from corner-sharing to edge-sharing. Based on the phenomenon ofthe crystallographic shear, a separation mechanism, that is, the metalfilm is formed of tungsten (W), and tungsten oxide (VI) (WO₃) is reducedto tungsten oxide (IV) (WO₂) by hydrogen, then, a film containing WO₃and WO₂, or a surface boundary between the film and another film issplit, will be explained. Firstly, the crystal structure of WO₃ and WO₂will be explained. WO₃ has a distorted oxide rhenium structure (AB₃,regular octahedron) having tungsten at the body center and oxygen at sixcorners (FIG. 1). WO₂ has a distorted rutile structure in which positiveions are positioned to the corners of a square and the body center andsix negative ions coordinate to the positive ion.

The non-stoichiometry of tungsten oxide is achieved by change in linkageof some octahedrons from corner-sharing into edge-sharing due to shear.The shear is occurred at a regular interval, and that is resulted thatregion of the rhenium structure is severed. In this regard, aggregate isformed of a plurality of octahedrons that share an edge. As justdescribed, the phenomenon that some octahedrons in the structure arechanged from corner-sharing to edge-sharing is observed in tungstenoxide. Tungsten oxide reacts tohydrogen, and becomes into tungsten oxide(V) (W₂O₅), W₄O₁₁, and further, tungsten oxide (IV) (WO₂), metaltungsten (W). In other words, metal tungsten reacts to hydrogen anddecreased in its valence number.

By the phenomenon of crystallographic shear and the property of tungstenoxide, reductive reaction is occurred due to hydrogen that is dispersedfrom an upper-layered film by heat treatment at 400° C. or more, andthen, the composition becomes changed. Change in composition is resultedto the change in crystal structure. Specifically, the oxide rheniumstructure changes into the distorted rutile structure and the insidestructure of tungsten oxide becomes distorted. Consequently, separationbecomes possible. In addition, it is considered that bond is broken dueto hydrogen dispersed from the upper-layered film, and a part ofcohesive force is decreased, then, the inside of tungsten oxide becomessusceptible to be broken.

The present invention composed of the above described constitution, TFTor the like can be formed over a flexible film substrate with goodyields since the whole surface separation can be carried out. Accordingto the present invention, there is no stress on TFT or the like. Alight-emitting apparatus, a liquid crystal display apparatus, andanother display apparatus are thin and hardly broken even if they fall.Further, display an image on a curved surface or unusual shape becomespossible. According to the present invention, a support or the like canbe reused and low cost film substrate is used, so that the cost of adisplay apparatus can be reduced by the synergistic effect.

The TFT formed according to the present invention can be employed in alight-emitting apparatus of top-emission, bottom-emission, anddual-emission, liquid crystal display apparatus of transparent type,reflective type, and translucent type, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a crystal structure of tungsten oxide;

FIG. 2 is a view showing a crystal structure of tungsten oxide;

FIGS. 3A to 3E are explanatory views showing a separation process;

FIGS. 4A to 4K are photographs showing experimental results;

FIGS. 5A and 5B are TEM images;

FIGS. 6A and 6B are a TEM image and a frame format of the TEM image;

FIGS. 7A and 7B are views showing a composition result of a film by XPS;

FIG. 8 is a view showing a profile by SIMS;

FIG. 9 is a view showing a profile by SIMS;

FIG. 10 is a view showing a profile by SIMS;

FIG. 11 is a view showing a result by TDS;

FIGS. 12A and 12B are a TEM image and a frame format of the TEM image;

FIGS. 13A and 13B are a TEM image and a frame format of the TEM image;

FIGS. 14A and 14B are a TEM image and a frame format of the TEM image;

FIGS. 15A and 15B are a TEM image and a frame format of the TEM image;

FIGS. 16A and 16B are a TEM image and a frame format of the TEM image;

FIGS. 17A and 17B are a TEM image and a frame format of the TEM image;

FIGS. 18A and 18B are an external view and a cross-sectional view of alight-emitting apparatus;

FIGS. 19A and 19B are an external view and a cross-sectional view of alight-emitting apparatus;

FIGS. 20A and 20B are an external view and a cross-sectional view of alight-emitting apparatus; and

FIGS. 21A to 21E are views showing electric appliances.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiment of the present invention will be described with reference toFIG. 3.

A metal film 11 is deposited over a first substrate 10 (FIG. 3A). Thefirst substrate (a support substrate) 10 has only to have rigidityenough to withstand a following separation process, for example, a glasssubstrate, a quartz substrate, a ceramic substrate, a silicon substrate,a metal substrate, or a stainless substrate can be used. As the metalfilm 11, a single layer or a laminated layer can be used that is formedof an element selected from the group consisting of W, Ti, Ta, Mo, Nd,Ni, Co, Zr, Zn, Ru, Rh, Pd, Os, or Ir; or an alloy material or acompound material, each of which contains the above described elementsas its main component. The thickness of the metal film 11 is from 10 to200 nm, preferably, from 50 to 75 nm. A metal nitride film can be usedinstead of the metal film 11.

The metal film 11 is deposited by face down sputtering, so that thethickness of the periphery of the first substrate 10 is susceptible tobe uneven. Therefore the film of a periphery portion is preferablyremoved, and an insulating film such as an oxynitride silicon film witha thickness approximately of 100 nm may be formed between the substrate10 and the metal film 11 to prevent the support substrate from beingetched back.

Subsequently, a release layer 12 is formed over the metal film 11. Therelease layer 12 has a first oxide 12 a and a semiconductor film 12 bincluding hydrogen. As the first oxide, silicon oxide, siliconoxynitride, or the like may be formed by sputtering, CVD. The thicknessof the first oxide is preferably to be twice as that of the metal film11. Here, a silicon oxynitride film is deposited to have a thickness offrom 150 to 200 nm by sputtering using a silicon target. A semiconductormay be provided with a TFT, an organic TFT, a thin film diode, a pinjunction photoelectric transfer device formed of silicon, a siliconresistance device, a sensor device (typically, a pressure sensitivefingerprint sensor), or the like. A base film formed of silicon nitrideor the like is preferably formed over the reverse side of thesemiconductor film included in the release layer 12 to shut outimpurities or dust from the metal film 11 or the first substrate (asupport substrate) 10.

A second oxide 17 exists between the metal film 11 and the release layer12. The second oxide is formed simultaneously with forming the firstoxide in the release layer 12. Taking tungsten as an example, it can beconsidered that tungsten oxide (WO_(X), the second oxide) is formed bypreferential oxidation reaction of oxygen with tungsten occurred at avery early stage during depositing the silicon oxide film (the firstoxide) by sputtering. Then, the second oxide (for example, WO₃) isreduced to form a third oxide (for example, WO₂), and a film containingthe second oxide and third oxide, or a surface boundary between anotherfilm is separated. Therefore, if the first oxide contains hydrogen, thereductive reaction is occurred in the second oxide, so that there is athreat that the second oxide is inhibited of its formation.Consequently, the first oxide is preferably formed not to containhydrogen. Specifically, when the second oxide contains hydrogen in caseof being formed by CVD, so that it is better not to use CVD.

Then, heat treatment is carried out at a temperature more than 400° C.The heat treatment causes reductive reaction in the second oxide, sincehydrogen, which is contained in the release layer 12, especially in asemiconductor, is diffused into another film. In addition, according tothe heat treatment, a part of or all of the second oxide iscrystallized. The heat treatment can be carried out together withanother manufacturing process to reduce the number of processes. Forexample, in case that an amorphous semiconductor is formed to form apolycrystalline semiconductor by a heating furnace or laser irradiation,hydrogen can be diffused simultaneously with crystallizing the amorphoussemiconductor by a heat treatment of at least 500° C.

Then, a second substrate 13 for supporting the release layer 12 isbonded with a first adhesive 14 (FIG. 3B). The rigidity of the secondsubstrate 13 is preferably higher than that of the first substrate 10.As the first adhesive 14, a bonding agent, a two-sided tape, or thelike, such as the adhesive that is peeled by UV light, the adhesive thatis peeled by heat, or the adhesive that is soluble in water can be used.

The first substrate 10 provided with the metal film 11 is separated by aphysical means (FIG. 3C). The first substrate 10 is separated bysplitting a film containing the second or third oxide, or a surfaceboundary with another film. According to this, the release layer 12 isseparated from the first substrate 10.

The separated release layer 12 is pasted to a third substrate 16 thatbecomes a transferred body with a second adhesive 15 (FIG. 3D). As thesecond adhesive 15, a UV cured resin, specifically, an epoxy resinadhesive, a resin additive adhesive, a two sided tape, or the like canbe used. As the third substrate 16, a flexible substrate having a thinfilm thickness (a film substrate), that is, a plastic substrate such aspolycarbonate, poly arylate, polyethersulfone, or the like; a Teflonsubstrate; a ceramic substrate; or the like is used.

Next, the second substrate 13 is separated by removing the firstadhesive 14 (FIG. 3E). Specifically, the first adhesive 14 can beseparated by UV light irradiation, heating, or water washing. Further,plasma cleaning with Ar gas or O₂ gas, or bellclean is preferablycarried out.

According to this, a TFT or the like formed over the film substrate thatis prepared as described above can be used for a semiconductor device ofa light-emitting apparatus or a liquid crystal display apparatus. Forexample, a light-emitting device is formed over the release layer 12,and a protective film that will serve as a sealing member, then, alight-emitting apparatus is completed. In order to form a light-emittingdevice over the release layer 12, a film substrate provided with TFTs isfixed to a glass substrate with a tape since the film substrate isflexible, and each light-emitting layer can be formed by vapordeposition. Note that a light-emitting layer, an electrode, a protectivefilm, and the like are preferably formed continuously without exposingto the atmosphere. The light-emitting apparatus can be, but notexclusively, manufactured in this order, that is, the light-emittingdevice is formed over the release layer, the second substrate is bonded,and the release layer having the light-emitting device is separated andpasted to the film substrate that serves as the third substrate.

A liquid crystal display apparatus may be, but not exclusively,manufactured in this order, that is, a second substrate is separated, anopposite substrate is bonded with a sealant, and a liquid crystalmaterial is injected. The liquid crystal display apparatus can bemanufactured in another order, that is, the second substrate is bondedas the opposite substrate, the third substrate is bonded, and the liquidcrystal material is injected. Spacers may be formed or dispersed inorder to keep the space between substrates when a liquid crystal displayapparatus is manufactured. In case of the flexible substrate, threetimes as many as spacers are preferably formed or dispersed.

According to the above described processes, thin films are depositedsequentially, and oxide formed at the surface boundary between the metalfilm and the oxide film are reduced and crystallized by heat treatmentat 400° C. or more, then, the oxide is separated by splitting the filmthat contains the oxide or the surface boundary between the film thatcontains the oxide and another film.

According to the present invention composed of the above describedconstitution, TFT or the like can be formed over a flexible filmsubstrate with good yields since the whole surface separation can becarried out. According to the present invention, there is no stress onTFT or the like. A light-emitting apparatus, a liquid crystal displayapparatus, and another display apparatus are thin and hardly broken evenif they fall. Further, display an image on a curved surface or unusualshape becomes possible. According to the present invention, a support orthe like can be reused and low cost film substrate is used, so that thecost of a display apparatus can be reduced.

EXAMPLE 1

As shown in above described embodiment, the experiment that isdemonstrated the fact that thin films are deposited sequentially, andoxide formed at a surface boundary between the metal film and the oxidefilm are reduced by heat treatment at 400° C. or more, then, the filmcontaining the oxide or a surface boundary between the film and anotherfilm is split will be explained hereinafter. In the followingexperiment, a tungsten film is used as the metal film, a silicon oxidefilm as the oxide film included in the release layer, and an amorphoussilicon film is used as the semiconductor film.

Experiment 1

AN 100 glass substrate (126×126 mm) as a substrate, a tungsten (W) film(50 nm) deposited by sputtering as a metal film, a silicon oxide film(200 nm) deposited by sputtering as a protective film, a siliconoxynitride (SiON) film (100 nm) deposited by CVD as a base film, and anamorphous silicon film (54 nm) deposited by CVD as a semiconductor filmare sequentially formed. Thereafter, samples 1 to 6, each of which areheat treated for 1 hour at 500° C., 450° C., 425° C., 410° C., 400° C.,and 350° C., and a sample 7, which is heat treated for 1 hour at 350° C.in the hydrogen atmosphere are prepared. Then, separation experimentsare respectively carried out to the samples 1 to 7 using apolytetrafluoroethylene tape. FIGS. 4A to 4G are photographs of theexperiments.

As shown in FIGS. 4A to 4G, samples 1 to 4, which are heat treated at410° C. or more can be separated, however, samples 5 and 6 cannot beseparated, that is, a semiconductor film or the like does not adhere tothe polytetrafluoroethylene tape.

FIGS. 4H and 4I are photographs showing both cases that heat treatmentfor 1 hour at 500° C. and separation are carried out, and heat treatmentfor 1 hour at 500° C. and for 4 hours at 550° C. and separation arecarried out as in the samples of 1 to 7 with respect to a sample 8provided with a semiconductor film. FIGS. 4J and 4K are photographsshowing both cases that heat treatment for 1 hour at 500° C. andseparation are carried out, and heat treatment for 1 hour at 500° C. andfor 4 hours at 550° C. and separation are carried out with respect to asample 9 provided with a silicon nitride (SiN) film (100 nm) instead ofa semiconductor film by CVD. As shown in FIGS. 4H to 4K, separation iscarried out to the case that heat treatment is carried out at for longhours 500° C. or more. Further, separation is carried out when either anamorphous semiconductor film or a silicon nitride film deposited by CVDis formed over the protective film.

According to the experiment, separation is carried out in case that heattreatment is carried out at 400° C. or more, and a film is deposited byCVD over the base film. In other words, the temperature of 400° C. isthe limit of acceptable temperature for carrying out separation.

Experiment 2

As in the case with the experiment 1, AN 100 glass substrate (126×126mm) as a substrate, a tungsten film (50 nm) deposited by sputtering as ametal film, a silicon oxide film (200 nm) deposited by sputtering as aprotective film, a silicon oxynitride (SiON) film (100 nm) deposited byCVD as a base film, and an amorphous silicon film (54 nm) deposited byCVD as a semiconductor film are sequentially formed. A sample A that isnot heat treated, a sample B that is heat treated for 1 hour at 220° C.,and a sample C that is heat treated for 1 hour at 500° C., and further,for 4 hours at 550° C. are prepared and TEM analysis is carried out.FIGS. 5A, 5B, and 6A are each TEM image, and FIG. 6B is a view showingthe frame format of each of the TEM image.

As shown in all TEM images, a new film (hereinafter, unknown film) isformed at a surface boundary between the tungsten film and the siliconoxide film. Compared with TEM images each other, only the unknown filmof the sample C has a crystal lattice arranged in a specific direction.The thickness of the unknown films of the samples A and B areapproximately 3 nm, but the thickness of the unknown film of the sampleC is slightly thinner than those of the samples A and B. Further, thesamples A to C are tried to be separated by a physical means such as atape and only sample C can be separated.

According to the experiment 2, an unknown film is formed at a surfaceboundary between the tungsten film and the silicon oxide film. Bycarrying out heat treatment at 500° C. or more as in the case with thesample C, the unknown film is crystallized. When the unknown film hascrystallinity, the sample becomes possible to be separated. Thethickness of the unknown film is uneven. Only the thickness of theunknown film of the sample C that is capable of being separated isslightly thin. Therefore, it is considered that whether the sample ispossible to be separated or not is related to the crystallinity and thethickness of the unknown film.

A table 1 is a quantitative measurement result by EDX for specifying thecomposition of the unknown films, which are found by above TEM images,in the samples A to C.

TABLE 1 Number of Element counts wt % atom % Sample A O 48 6.26 43.40 W1277 93.74 56.60 Sample B O 88 7.92 49.71 W 1816 92.08 50.29 Sample C O62 8.90 52.88 W 1127 91.10 47.12

As shown in the table 1, the unknown film is composed of tungsten (W)and oxygen (O). Therefore the unknown film is composed of WO_(x)(tungsten oxide) containing tungsten-mainly as its components. By thequantitative measurement result, a ratio of W to O of composition is W>Oin the samples A and B, and a ratio of W to O of composition is W<O inthe sample C.

According to the above experiment, a new film is formed at a surfaceboundary between the tungsten film (metal film) and the silicon oxidefilm (protective film). The film is formed of tungsten oxide containingtungsten as its main components. The composition ratios are differentbetween the samples A, B and the sample C.

Experiment 3

The composition of the tungsten oxide film in the samples A to C formedas in the case with the experiment 2 and the composition ratio of thetungsten film that is oxidized naturally as a comparison sample arestudied in an experiment 3 using XPS (X-ray Photoelectron Spectroscopy).A table 2 shows the result, and FIG. 7B shows the result in a bar graph.The table 3 shows a result of intensity of WO₂ and WO_(x) in case thatWO₃ is normalized by 100% with respect to the data in the result shownin the table 2. FIG. 7A is a bar graph showing the result. In thisexperiment, the internal of the unknown film is exposed by ionsputtering; let the case that tungsten is detected 1 (atomic %) be Pos.1; 2 (atomic %), Pos. 2; and 3 (atomic %), Pos. 3; and the compositionin depth is detected. The composition ratios of tungsten (W), tungstenoxide (IV) (WO₂), tungsten oxide (WO_(x), 2<X<3), tungsten oxide (IV)(WO₂) are detected with respect to each depth of Pos. 1 to 3. In-depthion sputtering is carried out to sample A at 4.25 minutes after, 4.5minutes after, and 4.75 minutes after; to sample B at 4.0 minutes after,4.25 minutes after, and 4.5 minutes after; and to sample C at 5.0minutes after, 5.25 minutes after, and 5.5 minutes after, respectively,and each of which corresponds to Pos. 1 to 3 in each the samples A to C.

As used herein, “tungsten oxide (WO_(x))” denotes WO₂, WO₃, W₂O₅, W₄O₁₁,W₂O₃, W₄O₃, W₅O₉, W₃O₈, or the like. Further, the term “naturallyoxidized film” denotes a tungsten film which is formed over a base filmon a glass substrate, and which is left in the atmosphere.

TABLE 2 Tungsten Tungsten Tungsten Tungsten Oxide Oxide Depth (W) Oxide(WO₂) (WO_(x)) (WO₃) Sample A Pos. 1 9.57 18.91 24.58 46.94 Pos. 2 12.5418.83 22.19 46.44 Pos. 3 14.45 20.49 21.49 43.57 Sample B Pos. 1 11.3219.68 22.42 46.58 Pos. 2 14.57 19.15 21.91 44.38 Pos. 3 15.46 21.2 22.1741.18 Sample C Pos. 1 35.51 16.37 16.13 32 Pos. 2 37.44 17.2 15.8 29.57Pos. 3 40.94 17.43 13.3 28.33 Natural Oxide Film 69.54 6.42 1.03 23.01

TABLE 3 Tungsten Tungsten Tungsten Depth Oxide (WO₂) Oxide (WO_(x))Oxide (WO₃) Sample A Pos. 1 40.29% 52.36% 100.00% Pos. 2 40.55% 47.78%100.00% Pos. 3 47.03% 49.32% 100.00% Sample B Pos. 1 42.25% 48.13%100.00% Pos. 2 43.15% 49.37% 100.00% Pos. 3 51.48% 53.48% 100.00% SampleC Pos. 1 51.16% 50.41% 100.00% Pos. 2 58.17% 53.43% 100.00% Pos. 361.52% 46.95% 100.00% Natural Oxide Film 27.90% 4.48% 100.00%

As shown in FIG. 7A and the table 2, the composition ratio of tungsten(W) is approximately 10 and several % in the samples A and B, though thecomposition ratio of tungsten (W) is at least 35% in depth in the sampleC. The composition ratio of tungsten oxide (WO₃) is approximately 45% inthe samples A and B, though the composition ratio of tungsten oxide(WO₃) is approximately 30% in depth in the sample C. Compared with thecomposition ratio between the samples A to C and naturally oxidizedfilm, the ratio of WO_(x) in the naturally oxidized film is extremelysmall.

As shown in FIG. 7B and the table 3, in which tungsten oxide (WO₃) is100%, the ratio of tungsten oxide (WO_(x)) is slightly higher than thatof tungsten oxide (WO₂) in the samples A and B, though the ratio oftungsten oxide (WO₂) is slightly higher than that of tungsten oxide(WO_(x)) in the sample C. Thus, it can be considered that thecomposition of tungsten oxide is changed by heat treatment.

According to this experiment, tungsten oxide is formed having acomposition ratio that is different from natural oxidation duringforming a silicon oxide film. Compared with the composition between thesamples A, B and the sample C, the ratio of tungsten is high andtungsten is low. Thus, in oxide in the sample C, it can be consideredthat the composition is changed due to some sort of reaction by heattreatment. It can be considered that differences among the samples A toC are the temperature of heat treatment, and the change in compositionof a metal oxide film in the sample C due to reductive reaction by heattreatment at 400° C. or more based on the results of experiments 1 and2. According to this, the fact that composition is changed correspondsto the fact that the crystal structure is different.

Experiment 4

FIGS. 8 to 10 are views showing SIMS (secondary ion mass spectrometry)profile with respect to the sample A to C used in the experiment 2.

Look at the profile of hydrogen (H) in an amorphous silicon film (a-Si),the concentration of hydrogen in the samples A, B is approximately1.0×10²² (aroms/cm³), and the concentration of hydrogen in the sample Cis approximately 1.0×10²⁰ (aroms/cm³), that is, the concentration ofhydrogen in the sample C is two orders of magnitude less than that inthe samples A, B. By observing hydrogen profile in a silicon oxynitridefilm (SiON) and a silicon oxide film (SiO₂), the hydrogen in the samplesA, B is decreased in the vicinity of 0.2 μm in depth. The concentrationdistribution is uneven. On the other hand, the sample C shows no signsof a prominent decrease, and the concentration distribution is even indepth. Therefore, in the sample C, hydrogen is dispersed evenly in depthin the silicon oxynitride film and the silicon oxide film. Next, look atthe concentration of nitride at the surface boundary between a siliconoxide film and a tungsten film (W), the concentration of nitride in thesamples A, B is approximately 1.0×10²¹ (aroms/cm³), and theconcentration of nitride in the sample C is approximately 6.5×10²¹(aroms/cm³). Therefore, as shown in the experiment 2, the composition ofthe unknown film over the surface boundary between the silicon oxidefilm and the tungsten film in the sample C is different from that in thesamples A, B.

On the other hand, FIG. 11 is a graph showing the relationship betweenthe density of desorbed hydrogen from an amorphous silicon film (a-Si)formed over a glass substrate and a substrate surface temperature (° C.)by Thermal Desorption Spectroscopy (TDS). As shown in FIG. 11, hydrogendesorbing from the amorphous silicon film is increased depending on anincrease in a substrate temperature. That is, hydrogen desorbs from theamorphous silicon film due to heat treatment at 400° C. or more.Therefore it can be considered that hydrogen in the amorphous siliconfilm is dispersed to another film by heat treatment at 400° C.

FIG. 11 shows the relationship between the density of desorbed hydrogenfrom a silicon nitride film (SiN) and a substrate surface temperature.As shown in FIG. 11, the hydrogen desorbed from the silicon nitride film(SiN) is increased depending on an increase in the substratetemperature.

Based on the results from SIMS and TDS, hydrogen in the amorphoussilicon film is dispersed due to heat treatment at 400° C. or more inthe sample C. Tungsten oxide (VI) (WO₃) reacts to hydrogen, and becomesinto tungsten oxide (V) (W₂O₅), W₄O₁₁, and further, tungsten oxide (IV)(WO₂), metal tungsten (W). According to this, reductive reaction isoccurred in the oxide of the sample C by hydrogen in the amorphoussilicon film that is dispersed by heat treatment at 400° C. or more. Asshown in FIG. 7, the composition of the sample C is different from thatof another sample.

Experiment 5

FIG. 12 is a TEM image showing the state that a tungsten film isdeposited over a glass substrate by sputtering to have a thickness of 50nm, and a silicon oxide film is deposited by sputtering thereon to havea thickness of 200 nm. FIG. 13 is a TEM image showing the state that isheat treated for 1 hour at 500° C. Both views show an surface boundarybetween the tungsten film and the silicon oxide film.

As shown in both views, a tungsten oxide film is formed at a surfaceboundary between the tungsten film and the tungsten oxide film. Unknownfilms in both views have almost same thickness of approximately 5 nm.Thus, the tungsten oxide film is formed independently from heattreatment and the film thickness is not influenced by the heattreatment. The tungsten oxide film is formed when the tungsten film andthe tungsten oxide film are stacked. Next, compared with the crystalstate of unknown films in FIGS. 12, 13 each other, the crystal latticein FIG. 12 is uneven, but a part of the crystal lattice in FIG. 13 isformed even in certain direction. That is, the crystal state of thetungsten oxide film is dependent on heat treatment. Therefore an evensized crystal lattice is formed in the unknown film formed when thetungsten film and the tungsten oxide film are stacked by heat treatment.

In the lamination structure used in this experiment, the tungsten filmis tried to be separated from the silicon oxide film at their surfaceboundary by a physical means such as a tape, but failed. Thus,separation is impossible in this manufacturing process in which thetungsten film and the tungsten oxide film are stacked, and heattreatment is carried out.

According to this experiment, oxide is crystallized by heat treatment,however, separation is impossible since reductive reaction is notoccurred in the oxide in case that the heat treatment is not carried outafter a film containing hydrogen is formed.

Experiment 6

In this experiment, four samples are prepared: a sample D formed bylaminating over a glass substrate a silicon oxynitride film deposited asa base film by CVD and a tungsten film (W) deposited with a thickness of50 nm as a metal film by sputtering; a sample E formed of an amorphoussilicon film deposited as a protective film by sputtering using argongas over the tungsten film; a sample F formed of a silicon oxide filmdeposited by sputtering using argon gas and oxygen gas over the tungstenfilm; and a sample G formed of a silicon oxide film deposited by CVDusing silane gas and nitride gas over the tungsten film.

FIGS. 14A to 17A are TEM images showing cross-sectional views of eachsamples D to G. FIGS. 14B to 17B are frame formats showing each samplesD to G. Look at a surface boundary between a tungsten film and an upperfilm of the tungsten film, a naturally oxidized film is formed over thetungsten film of the sample D in FIG. 14A, however, the thickness is toothin to be detected in the TEM image. A metal oxide film is not formedover tungsten films of the sample E in FIG. 15A and the sample G in FIG.16A, however, a metal oxide film is formed over the tungsten film of thesample F. Thus, the metal oxide film is formed only over the tungstenfilm of the sample F. It can be considered that the metal oxide film isformed at an early stage of forming the silicon oxide film bypreferential oxidative reaction of oxygen and tungsten due to oxygen gasused for forming the film. Based on the fact, the metal oxide film isnot formed over the tungsten film in the sample E since only argon gasis used for a film formation.

Compared with the state of film formation between the sample F and thesample G, argon gas and oxygen gas are used in the sample F, and silanegas and N₂O gas are used in the sample G. That is, the metal oxide filmis not detected in the sample G by the reduction of the silicon oxidefilm formed between the tungsten film and silicon oxide film due tohydrogen since silane gas contains hydrogen.

According to this experiment, when the silicon oxide film is formed overthe tungsten film, the metal oxide film is formed over the surfaceboundary between the silicon oxide film and the tungsten film. However,if gas containing hydrogen is used for forming a protective film, ametal oxide film is not formed at its surface boundary. The reason isthat tungsten oxide (VI) (WO₃) reacts to hydrogen, and becomes intotungsten oxide (V) (W₂O₅), W₄O₁₁, and further, tungsten oxide (IV)(WO₂), metal tungsten (W) so that reductive reaction is occurred in theformed metal oxide film.

EXAMPLE 2

A light-emitting apparatus provided with TFTs fabricated over a filmsubstrate by the separation method according to the present inventionwill be explained with reference to FIG. 18.

FIG. 18A is a top view of the light emitting apparatus, referencenumeral 1210 denotes a film substrate; 1201, a signal line drivercircuit; 1202, a pixel portion; and 1203, a scanning line drivercircuit.

FIG. 18B is a cross-sectional view taken along a line A-A′ of FIG. 18A.An oxide layer 1250 is formed over the film substrate 1210 via anadhesive 1240. The signal line driver circuit 1201 having a CMOS circuitcomposed of an n-channel TFT 1223 and a p-channel TFT 1224 is formedover the film substrate 1210. A TFT constituting a signal line drivercircuit and a scanning line driver circuit can be formed by a CMOScircuit, a PMOS circuit, or an NMOS circuit. In this embodiment, adriver integrated type in which a signal line driver circuit and ascanning line driver circuit are formed over a substrate is described,but not exclusively, these circuits can be formed outside of thesubstrate.

A pixel portion 1220 is illustrated comprising an insulator 1214 thathas a switching TFT 1221 and a current control TFT 1212, and that coversthe switching TFT 1221 and the current control TFT 1212, and that has anopening portion in the prescribed position; a first electrode 1213connected to one of wirings of the current control TFT 1212; organiccompound layer 1215 formed over the first electrode; a light-emittingdevice 1218 having a second electrode 1216 that is opposed to the firstelectrode; and a protective layer 1217 for preventing deterioration ofthe light-emitting device due to moisture and oxygen.

Since the first electrode 1213 is connected to the drain of the currentcontrol TFT 1212, at least lower side of the first electrode 1213 ispreferably formed by the material that can make ohmic contact with thedrain region of a semiconductor film, and the surface that is contact tothe organic compound layer is preferably formed by a material having alarge work function. For example, in case that a three-layer structurecomposed of a titanium nitride film, a film containing aluminum as itsmain components, and a titanium film is adopted, resistance as a wiringis low and favorable ohmic contact can be made. The first electrode 1213can be formed into a single layer formed of a titanium nitride film, andformed into a three or more layers structure. Further, if a transparentconductive film is used for the first electrode 1213, a dual emissiontype light-emitting apparatus can be manufactured.

The insulator 1214 can be formed of an organic resin film or aninsulating film containing silicon. Here, a positive type photosensitiveacrylic resin film is used for forming the insulator 1214.

For improving a coverage effect, an upper edge portion or a lower edgeportion of the insulator 1214 is preferably formed to have a curvedsurface having a curvature. For example, when the positive typephotosensitive acrylic resin is used as a material for the insulator1214, only the upper edge portion of the insulator 1214 is formedpreferably to have a curved surface having a radius of curvature (0.2 to3 μm). As for the insulator 1214, either a negative type which becomesinsoluble to an etchant by photosensitive light, and a positive typewhich becomes soluble to the etchant by light can be used.

Further, the insulator 1214 may be covered by a protective film formedof an aluminum nitride film, an aluminum nitride oxide film, or asilicon nitride film. The protective film is an insulating filmcontaining silicon nitride or silicon nitride oxide as its maincomponents deposited in a film formation system by sputtering (DC typeor RF type) or remote plasma, or a thin film containing carbon as itsmain components. The thickness of the protective film is preferablyformed into thin as much as possible to pass light through theprotective film.

An organic compound layer 1215 is selectively deposited over the firstelectrode 1213 by vapor deposition using an evaporation mask, or anink-jetting. Further, a second electrode 1216 is formed over the organiccompound layer 1215. A color filter composed of a coloring layer and aBM is provided to light-emitting device 1218 since the light-emittingdevice 1218 emits white light.

If organic compound layers each of which emits light of R, G, B areselectively formed, full color display can be achieved without using thecolor filter.

The second electrode 1216 is connected to a connecting wiring 1208 viaan opening portion (contact) provided with the insulator 1214 in aconnecting region. The connecting wiring 1208 is connected to a FPC(flexible printed circuit) 1209 by an anisotropic conductive resin. Theconnecting wiring 1208 receives a video signal and a clock signal fromthe FPC 1209 that serves as an external input terminal. A printed wiringboard (PWB) can be attached to the FPC.

A sealing agent 1205 is provided to the periphery of the substrate topaste second film substrate 1204 to the substrate and to seal thelight-emitting device. An epoxy resin is preferably used for the sealingagent 1205.

In this embodiment, a plastic substrate made of fiberglass-reinforcedplastics (FRP), polyvinyl fluoride (PVF), Mylar, polyester, an acrylicresin, or the like, in addition to a glass substrate or a quartzsubstrate, can be used as a material for forming the second filmsubstrate 1204.

Although not shown in the drawings, a barrier film formed of an organicmaterial such as polyvinyl alcohol, or ethylene-vinylalcohol copolymer;an inorganic material such as polysilazane, aluminum oxide, siliconoxide, or silicon nitride; or a lamination layer formed of thesematerials may cover the film substrate to prevent moisture and oxygenfrom penetrating into the film substrate.

Further, a protective layer can be formed to prevent chemicals during amanufacturing process. As a material for forming the protective layer, aUV cured resin or a thermal cured resin can be used.

Accordingly, a light-emitting apparatus having TFTs over a filmsubstrate is completed. The light-emitting apparatus having TFTsaccording to the present invention is lightweight, and is hardly brokeneven if the apparatus falls. Using the film substrate makes it possibleto grow the light-emitting apparatus in size for a mass-production.

EXAMPLE 3

A liquid crystal display apparatus provided with TFTs formed over a filmsubstrate by a separation method according to the present invention willbe explained with reference to FIG. 19.

FIG. 19A is a top surface view of a liquid crystal display apparatus.Reference numeral 1310 denotes a first film substrate; 1301, a signaldriver circuit; 1303, a scanning driver circuit; and 1302, a pixelportion.

FIG. 19B is a cross-sectional view of a liquid crystal display apparatustaken along the line A-A′. A oxide layer 1350 is formed over the filmsubstrate 1310 via an adhesive 1340. Reference numeral 1301 denotes asignal line driver circuit 1301 provided with a CMOS circuit composed ofan n-channel TFT 1323 and a p-channel TFT 1324 over the film substrate1310. A TFT constituting a signal line driver circuit and a scanningline driver circuit can be formed by a CMOS circuit, a PMOS circuit, oran NMOS circuit. In this embodiment, a driver integrated type in which asignal line driver circuit and a scanning line driver circuit are formedover a substrate is described, but not exclusively, these circuits canbe formed outside of the substrate.

The pixel portion 1302 is illustrated that it includes an interlayerinsulating film 1314 having a switching TFT 1311 and a retention volume1312 and covering the switching TFT 1311 and the retention volume 1312.

An oriented film 1317 is formed over the interlayer insulating film 1314and subjected rubbing treatment.

A second film substrate 1304 is prepared as an opposing substrate. Thesecond film substrate 1304 comprises a color filter 1330 in the regionthat is divided in matrix configuration by resin or the like, anopposing electrode 1316, and the oriented film 1317.

A deflecting plate 1331 is provided over the first and the second filmsubstrate and bonded thereto with a sealant 1305. A liquid crystalmaterial 1318 is infected between the first and the second filmsubstrate.

Although not shown in the drawings, barrier film formed of an organicmaterial such as polyvinyl alcohol, or ethylene-vinylalcohol copolymer;an inorganic material such as silicon oxide; or a lamination layerformed of these materials may cover the film substrate to preventmoisture and oxygen from penetrating into the film substrate.

Further, a protective layer can be formed to prevent chemicals during amanufacturing process. As a material for forming the protective layer, aUV cured resin or a thermal cured resin can be used.

As in FIG. 18, the film substrate connects to a wire and a FPC byanisotropic conductive resin and receives a video signal, clock signal,and the like.

Accordingly, a light-emitting apparatus having TFTs over a filmsubstrate is completed. The light-emitting apparatus having TFTsaccording to the present invention is lightweight, and is hardly brokeneven if the apparatus falls. Using the film substrate makes it possibleto grow the light-emitting apparatus in size for a mass-production.

EXAMPLE 4

An example of the present invention will be explained with reference toFIG. 20. A panel installed with a pixel portion and a driver circuit forcontrolling the pixel portion over one insulating surface; and a memorycircuit and a CPU will be explained in this example.

FIG. 20 is an external view of a panel. The panel has a pixel portion3000 composed of a plurality of pixels arranged in a matrixconfiguration over a substrate 3009. A scanning line driver circuit 3001for controlling the pixel portion 3000 and a signal line driver circuit3002 are formed at the periphery of the pixel portion 3000. The pixelportion 3000 displays an image depending on signals transmitted from thedriver circuit. An opposing substrate can be provided over only thepixel portion 3000, the driver circuits 3001, and 3002, and also overthe whole surface. In case of providing the substrate over the CPU 3008,note that the opposing substrate is preferably arranged to make a heatradiation sheet contact with the CPU 3008 since the CPU may generateheat. Further, the panel also has a VRAM 3003 (video random accessmemory) for controlling the driver circuits 3001, 3002, and decoders3004, 3005 at the periphery of the VRAM 3000. In addition, the panel hasa RAM (random access memory) 3006, a decoder 3007 at the periphery ofthe RAM 3006, and the CPU 3008. All devices composing a circuit over thesubstrate 3009 are formed of polycrystalline semiconductor (polysilicon)that has higher field-effect mobility and larger ON current than that ofamorphous semiconductor. Therefore a plurality of circuits can be formedinto an integrated circuit over one insulating surface. A pixel portion3001, a driver circuits 3001, 3002, and another circuit are formed overa support substrate, and peeled by the separation method according tothe present invention, then, pasted each other to realize an integratedstructure over a flexible substrate 3009. The structure of the pluralityof pixels in the pixel portion is, but not exclusively, formed byproviding SRAM to each the plurality of pixels. According to this, VRAM3003 and RAM 3006 can be omitted.

Next, the structure of the CPU is briefly explained. The CPU has acontrol unit and an arithmetic circuit. Upon inputting opcode to a databus 3020 for inputting and outputting data such as values used for anoperation result and an operation, and instructions, instructions areonce stored in a resistor 3022 via a data bus interface 3021, andanalyzed in a decoder 3023. Then, each control signal is generated in acontrol unit 3024, and memory read cycle, memory write cycle, and thelike are carried out depending on the inputted opcode. In addition, theCPU has a resistor array 3025 that is a memory used in the CPU, and thatserves as an internal resistor, ALU 3026 for arithmetical operation andlogical operation, a logic and buffer 3027 for controlling an output ofaddress and buffer, and an address bus 3028 for inputting and outputtingaddress such as a memory space.

The driver circuits 3001, 3002, and the CPU 3008 can be provided to theexterior of the substrate 3009. Here, a plurality of circuits are formedover the insulating surface, but circuits can be formed into a narrowframe shape by building up semiconductor devices. For example, pixelportions for displaying images are stacked over a circuit such as a CPU,and such structure will be more helpful for electric appliances that arerequired to be downsizing and lightweight.

EXAMPLE 5

The present invention can be applied to various electric appliances.Given as examples as the electric appliances: a personal digitalassistance (a cellular phone, a mobile computer, a portable gamemachine, an electronic book, or the like), a video camera, a digitalcamera, a goggle type display, a display, a navigation system, and thelike. FIGS. 21A to 21E are views showing these electric appliances.

FIG. 21A shows a display having a frame 4001, a sound output unit 4002,a display unit 4003, and the like. The present invention is used to thedisplay unit 4003. The display includes all information displayapparatus such as a personal computer, a TV broadcasting, and anadvertisement display. FIG. 21B shows a mobile computer having a mainbody 4101, a stylus 4102, a display unit 4103, an operation button 4104,an external interface 4105, and the like. The present invention is usedto the display unit 4103.

FIG. 21C shows a game machine having a main body 4201, a display unit4202, an operation button 4203, and the like. The present invention isused to the display unit 4202. FIG. 21D is a cellular phone having amain body 4301, a sound output unit 4302, a sound input unit 4303, adisplay unit 4304, an operation switch 4305, an antenna 4306, and thelike. The present invention is used to the display unit 4304. FIG. 21Eshows a electronic book reader having a display unit 4401, and the like.The present invention is used to the display unit 4401.

The application range of the present invention is extremely large, sothat the present invention can be used to various electric appliances inmany fields. Especially, the present invention that enables apparatus tobe thin film and lightweight are helpful for the electric appliancesillustrated in FIGS. 21A to 21E.

1. A method for manufacturing a semiconductor device comprising: forminga metal film over a first substrate; forming an oxide film over themetal film; forming at least a transistor including a semiconductor filmcontaining hydrogen over the oxide film; forming an insulating film overthe transistor; bonding a second substrate to the insulating film;separating at least the transistor and the insulating film from thefirst substrate by heating to diffuse hydrogen contained in thesemiconductor film and reducing metal oxide formed at a surface boundarybetween the metal film and the oxide film.
 2. A method according toclaim 1, wherein the transistor and the insulating film are separatedfrom the first substrate in the reduced metal oxide, a surface boundarybetween the reduced metal oxide and the metal film, or a surfaceboundary between the reduced metal oxide and the oxide film.
 3. A methodaccording to claim 1, wherein the metal film is formed of an elementselected from the group consisting of W (tungsten), Ti (titanium), Mo(molybdenum), Cr (chrome), Nd (neodymium), Fe (iron), Ni (nickel), Co(cobalt), Zr (zirconium), Zn (zinc), Ru (ruthenium), Rh (rhodium), Pd(palladium), Os (osmium), Ir (iridium); a single layer formed of analloy material or a compound material, each of which contains the aboveelements as its main components; or a lamination layer formed of thesemetals or mixture of these metals.
 4. A method according to claim 1,wherein the heating treatment is carried out at 400° C. or higher.
 5. Amethod according to claim 1, wherein the reduced metal oxide and themetal oxide are crystallized.
 6. A method according to claim 1, whereinthe oxide film is formed of a silicon oxide film deposited bysputtering.
 7. A method according to claim 1, wherein the semiconductorfilm is formed of a silicon film deposited by CVD.
 8. A method formanufacturing a semiconductor device comprising: forming a metal filmover a first substrate; forming an oxide film over the metal film;forming at least a transistor including a nitride film containinghydrogen over the oxide film; forming an insulating film over thetransistor; bonding a second substrate to the insulating film;separating at least the transistor and the insulating film from thefirst substrate by heating to diffuse hydrogen contained in the nitridefilm and reducing metal oxide formed at a surface boundary between themetal film and the oxide film.
 9. A method according to claim 8, whereinthe transistor and the insulating film are separated from the firstsubstrate in the reduced metal oxide, a surface boundary between thereduced metal oxide and the metal film, or a surface boundary betweenthe reduced metal oxide and the oxide film.
 10. A method according toclaim 8, wherein the metal film is formed of an element selected fromthe group consisting of W (tungsten), Ti (titanium), Mo (molybdenum), Cr(chrome), Nd (neodymium), Fe (iron), Ni (nickel), Co (cobalt), Zr(zirconium), Zn (zinc), Ru (ruthenium), Rh (rhodium), Pd (palladium), Os(osmium), Ir (iridium); a single layer formed of an alloy material or acompound material, each of which contains the above elements as its maincomponents; or a lamination layer formed of these metals or mixture ofthese metals.
 11. A method according to claim 8, wherein the heatingtreatment is carried out at 400° C. or higher.
 12. A method according toclaim 8, wherein the reduced metal oxide and the metal oxide arecrystallized.
 13. A method according to claim 8, wherein the oxide filmis formed of a silicon oxide film deposited by sputtering.
 14. A methodaccording to claim 8, wherein the semiconductor film is formed of asilicon film deposited by CVD.
 15. A method for manufacturing asemiconductor device comprising: forming a metal film over a firstsubstrate; forming an oxide film over the metal film; forming at least atransistor including a semiconductor film containing hydrogen over theoxide film; forming an insulating film over the transistor; heating todiffuse hydrogen contained in the semiconductor film and reducing metaloxide formed at a surface boundary between the metal film and the oxidefilm, bonding a second substrate to the insulating film; separating atleast the transistor and the insulating film from the first substrate.16. A method according to claim 15, wherein the transistor and theinsulating film are separated from the first substrate in the reducedmetal oxide, a surface boundary between the reduced metal oxide and themetal film, or a surface boundary between the reduced metal oxide andthe oxide film.
 17. A method according to claim 15, wherein the metalfilm is formed of an element selected from the group consisting of W(tungsten), Ti (titanium), Mo (molybdenum), Cr (chrome), Nd (neodymium),Fe (iron), Ni (nickel), Co (cobalt), Zr (zirconium), Zn (zinc), Ru(ruthenium), Rh (rhodium), Pd (palladium), Os (osmium), Ir (iridium); asingle layer formed of an alloy material or a compound material, each ofwhich contains the above elements as its main components; or alamination layer formed of these metals or mixture of these metals. 18.A method according to claim 15, wherein the heating treatment is carriedout at 400° C. or higher.
 19. A method according to claim 15, whereinthe reduced metal oxide and the metal oxide are crystallized.
 20. Amethod according to claim 15, wherein the oxide film is formed of asilicon oxide film deposited by sputtering.
 21. A method according toclaim 15, wherein the semiconductor film is formed of a silicon filmdeposited by CVD.
 22. A method for manufacturing a semiconductor devicecomprising: forming a metal film over a first substrate; forming anoxide film over the metal film; forming at least a transistor includinga nitride film containing hydrogen over the oxide film; forming aninsulating film over the transistor; heating to diffuse hydrogencontained in the nitride film and reducing metal oxide formed at asurface boundary between the metal film and the oxide film, bonding asecond substrate to the insulating film; separating at least thetransistor and the insulating film from the first substrate.
 23. Amethod according to claim 22, wherein the transistor and the insulatingfilm are separated from the first substrate in the reduced metal oxide,a surface boundary between the reduced metal oxide and the metal film,or a surface boundary between the reduced metal oxide and the oxidefilm.
 24. A method according to claim 22, wherein the metal film isformed of an element selected from the group consisting of W (tungsten),Ti (titanium), Mo (molybdenum), Cr (chrome), Nd (neodymium), Fe (iron),Ni (nickel), Co (cobalt), Zr (zirconium), Zn (zinc), Ru (ruthenium), Rh(rhodium), Pd (palladium), Os (osmium), Ir (iridium); a single layerformed of an alloy material or a compound material, each of whichcontains the above elements as its main components; or a laminationlayer formed of these metals or mixture of these metals.
 25. A methodaccording to claim 22, wherein the heating treatment is carried out at400° C. or higher.
 26. A method according to claim 22, wherein thereduced metal oxide and the metal oxide are crystallized.
 27. A methodaccording to claim 22, wherein the oxide film is formed of a siliconoxide film deposited by sputtering.
 28. A method according to claim 22,wherein the semiconductor film is formed of a silicon film deposited byCVD.